Spark, compression and fuel but no start

Kneedown1981 · Derestricted Danger Joined: 16 Apr 2019 Karma :

Hi guys

So as per title really, I have a zx6r f3, bike was running fine, then while sitting idling suddenly started to run on 3 cylinders.

Turned off left for a while and now bike will not start at all.

Removed carbs and cleaned thoroughly, drained fuel, did compression test on all cylinders and they are in spec, plugs are sparking when removed and placed against frame.

Won’t even fire on easy start, turns over fine and plugs get wet but will not ignite. I’m starting to think the spark timing or spark strength is the issue.
My question is will the plugs still spark with a fault on the pickup coil or even the coil pack. Because it went to three I am thinking it’s a possible electrical issue relating to the coil pack and will start testing with the Multimeter.

All safety switches are doing what they should, the shutoff systems On this bike won’t allow the bike to turn over if they are engaged and it turns over fine. However when I crank the engine the tacho needle does not move at all, and from memory it should.
Am also thinking could be a bad ground but want to see what people think and get some ideas.

Thanks for any help guys

bradh511 · Scooby Slapper Joined: 01 May 2009 Karma :

sounds like a spark issue if has comp and wont run on easy start ..

check ht leads are not arking on the top of the cylinder head best done in a dark garage. if not further investigation of coil and cdi unit will be necessary

i doubt to coils would go at the same time unless someone been leaving ingtion on to burn them out.
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Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013 Smile

BusterGonads · Trackday Trickster Joined: 18 May 2018 Karma :

Check again for spark.

If the bike has compression AND spark AND easystart it has to run assuming the spark is timed right, and we can assume it is because the bike was running.

The suggestion made earlier about HT arcing is a good one.

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

Do you have/can make fir those red neon plug caps so you can "see" the ht flash in real world conditions?? as a test.

you have a multi meter for resistance checks etc.??

get a wiring diagram.

you know of cmsnl for its exploded views which can only help etc.
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nuts about bikes

hawkeyefxr · L Plate Warrior Joined: 18 Aug 2019 Karma :

Having a spark at the plugs out of the head so you can see the spark is not the same as under compression, but it's hard to believe this would happen on all cylinders.
You need to know if it is sparking under compression.
Check the leads and cap as these things that were disturbed when you changed the plugs.
Not sure what HT leads you have, they may well be carbon ones,, there is not a lot you can do about checking these. Copper core ones you could bare the ends and clamp them direct to the plugs, but don't ride around like this as i think it's illegal. Causes interference with things.
Try and find the resistance reading for your coils fore for the HT and 12v supply side of the coils. You can then check them with a multimeter.
The other thing is i have heard that there are fake plugs now, it was on the beeb.

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

It was running fine - so we can rule out anything mechanical, or a cock-up on a top end rebuild setting the valve timing wrong. I'll rule out compression as well, because it's a 4 and it would be unlikely to lose compression on all 4 cylinders at once.

Fuel is unlikely to be a problem, although if it has a fuel filter I would check/change it just in case. It was running, presumably in regular use, so the carbs are clean. Fuel cleans carbs.

So that leaves electrical. Favourite places for things to go wrong are:
1. Rusty/corroded earthing points. Find them and clean them up. For a quick diagnosis or easy bodge, run a wire from one of the crankcase bolts to the battery negative terminal and see if it starts behaving.

2. Regulator/rectifier, because they are just universally shit and pretty much a service item. Charge the battery. If it then starts, check the voltage of the battery with it running. 14.5V at 4000rpm is good. Less than 13 is bad.

3. Spark plugs, because despite the massive advances in technology and people saying they should last for ages, changing the plugs still seems to solve enough problems to be worth trying. Bikes do work their plugs hard, to be fair.

Try these simple bits before looking for more complex problems.